In current wireless communication systems, after processing a signal received from a network node (e.g., base station, NodeB, eNB, etc.), a user equipment (UE) may generate and transmit an acknowledgement (ACK) or negative acknowledgement (NACK) to the network node as feedback indicating whether the received signal has been successfully received. In some of these systems, the UE may generate and transmit the ACK/NACK (“AN” or “A/N”) signal within the same slot during which the downlink signal was received. For this same-slot ACK/NACK signal transmission to occur, the processing time required for the UE to generate the ACK/NACK signal typically must be less than the time that remains in the slot (minus residual time, e.g., time required for actual uplink ACK/NACK transmission) following the symbol during which the downlink signal was transmitted by the network node and received by the UE.
As this processing time is typically longer than an Orthogonal Frequency Division Multiplexed (OFDM) symbol in a slot (e.g., containing seven OFDM symbols), a conservative gap of multiple OFDM symbols in the uplink/downlink frame structure is created in some implementations to allow the UEs in communication with a network node temporary on-demand access to the medium (e.g., one or more carriers utilized for UE-network node communication over a certain time period) for transmitting the ACK/NACK signal after its requisite processing is completed. In instances where the ACK/NACK signal processing time is relatively long (e.g., greater than two OFDM symbols), a substantial system performance opportunity cost may arise as a result of the medium being effectively unused as UEs and network nodes of the system await ACK/NACK processing resolution.
Thus, improved uplink control frame structures and related techniques for uplink control signal transmission are needed to optimize performance and resource utilization relative to those of existing systems.